Gene profiling technology has enabled analysis of the transcriptome and proteome of tumor cells. This information has provided useful information with regard to molecular mechanisms that define the enhanced survival and proliferation of MM cells. However, an equally, if not more important, goal is to define those proteins that participate in signaling pathways active in MM cells and their supporting stroma. Enzymes that phosphorylate tyrosine, serins and threonine residues on other proteins play a major role in signaling cascades that determine cell cycle entry and survival in MM and the stromal cells that support them. In particular, knowing the signaling pathways that are active in MM cells and their supporting stroma will provide critical information for understanding MM cell survival in the BM. We have developed and are applying to purified cells a novel array-based strategy that allows the simultaneous detection of phosphorylation for 1152 different kinase substrates. Here we propose to apply this emerging technology to the analysis of phosphorylation-based cell signaling pathways in MM and their supporting stroma. This R21/R33 Phased Innovation application will be pursued in two phases. In the R21 phase of this application Aims 1 and 2 will validate that PepChip technology can be applied to MM cells and their microenvironment to reveal signaling alterations in MM. In Aim 3 of the R33 phase we will use PepChip technology to identify kinome alterations within the MM patient population that are correlated with clinical parameters such as relapse and chromosomal abnormalities associated with poor prognosis. In Aim 4 we will utilize an in vivo model that supports the growth of primary patient isolates in RAG2XGammaC mice to determine the effect of therapeutics on the kinome of MM cells. This study will be pursued in the following.phased R21/R33 format: R21 Phase: Aim 1: Define the kinome of MM cells and normal plasma cells. Aim 2: Define differences in the microenvironmental kinome of MM and normal BM. R33 Phase: Aim 3: Identify kinome alterations in MM correlated with clinical parameters of disease. Aim 4: Identify kinome alterations in MM cells in response to therapeutics in vivo. [unreadable] [unreadable] [unreadable]